1. Field of the Invention
This invention relates to an automatic test sample handling system. More particularly, it relates to a system in which a plurality of test samples are automatically and selectively presented to a test probe for analysis by an instrument connected to the probe.
2. Prior Art
There currently exists a wide variety of analytical instruments that use test probes for detecting some characteristic associated with a test sample and providing an electrical analog signal proportional to the characteristic. A specific example is a spectrophotometer having a fiber optic light system designed to project light onto or through a sample and measure the reflectance or transmittance thereof across a spectrum of different or discrete wavelengths.
In the past, many such instruments were designed to have an individual test sample manually prepared and handled so as to be presented to the test probe. More recently, there has been a trend to providing automatic sample handling systems which are capable of handling a plurality or multiplicity of test samples in which the samples have been previously prepared for analysis. In such systems, the automatic sample handling allows the various tests to be made at a relatively high throughput rate. Some of these systems include some form of a program controlled digital electronic controller that controls the operation of a transport mechanism having some form of stepping motors that selectively move the samples through the test station.
While such instruments are capable of testing a wide variety of materials, the instruments find multiple applications for analyzing liquid samples in which the sample is contained within a test tube. Generally, testing procedures associated with such liquid samples involve two phases, the sample preparation phase and the actual testing. A more specific example to illustrate both phases deals with the use of colorimetric reagents to detect or measure the concentration of a substance within the liquid. Here, the sample preparation includes adding the reagent to the sample. After the reagent has sufficient time to react with the sample and reach a stable level, the resultant test sample is then analyzed by a spectrophotometer to determine the color characteristics thereof. These color characteristics are proportional to the concentration of the substance being analyzed. Analyses and tests of this nature are well known and described within the current literature. See for example, "Instrumental Methods of Analysis", Fifth Edition, by H. H. Willard et al, published by D. VanNostrand Co., New York. An example of an automatic spectrophotometric sample system is disclosed in U.S. Pat. No. 3,704,953 -- Carter et al. Examples of automatic test tube transport or handling systems are disclosed in U.S. Pat. Nos. 3,687,632 -- Natelson and 3,768,526 - Sanz et al.